I’m not quite sure. What you said could be true for me. I’ve also noticed that I speak better when I don’t think about what I’m about to say. When im relaxed and talking to someone im comfortable with I tend to think and plan what im going to say next and that causes the blocks. When im speaking while under pressure or to a crowd I tend to speak without thinking so it just flows better.. it’s more off the top of my head rather than planned out.